Automatic power control (APC) of light emitting devices allows for a constant and a consistent output from these devices. Generally, automatic power control of edge emitting laser devices is easily achieved because edge emitting devices emit light from two ends. Thus, enabling one of the light emitting ends to be used to measure the power output, which is subsequently use to adjust the power input to the edge emitting device, thereby adjusting the power output.
However, automatic power control of a vertical cavity surface emitting laser (VCSEL) is a difficult task because the VCSEL generally emits light from only a single surface, thus making measurement of the output and subsequent adjustment thereof a difficult task. Conventionally, in order to accomplish this task, several optical devices, such as photodiodes, mirrors, beam splitters, and the like are positioned in the optical path of the emission from the VCSEL. To maintain a given output power from a VCSEL it has been previously proposed to integrate a photodetector with the device structure and collect a portion of the lasing light that can then be used in a feedback control system to maintain a constant output power. Each individual VCSEL includes its own photodetector and control circuitry.
Many future applications utilizing VCSEL technology, include VCSEL arrays such as those preferred in parallel data storage, printing and data communications applications. In all of these applications it is advantageous if the output power from each individual VCSEL device of the VCSEL array be maintained at a constant value that is independent of such things as the ambient temperature or age of the actual VCSEL device. Effects such as increasing temperature and aging generally reduce the level of output power from a given output power of a VCSEL device and as such this impacts the performance of the laser device in any given system. However, individual APC of each VCSEL device in a VCSEL array has not been addressed.
It can be readily seen that conventional APC technology of VCSEL devices does not easily enable the automatic power control of individual VCSEL devices which compose an array of VCSELs. Therefore, an integrated article and method for making a VCSEL array with integrated photodetectors for automatic power control of each individual VCSEL device of the array would be highly desirable.
It is a purpose of the present invention to provide a new and improved integrated VCSEL array and photodetector for automatic power control of each individual VCSEL in the array.
It is another purpose of the present invention to provide a new and improved integrated VCSEL array and photodetector which is simple and relatively inexpensive to manufacture
It is still another purpose of the present invention to provide a new and improved integrated VCSEL array and photodetector which are integrated with a minimum of labor and cost.
It is a further purpose of the present invention to provide a new and improved integrated VCSEL array and photodetector which can be utilized to control the output of each individual VCSEL device which composes the array.